How to replace a word in dataframe by using another dataframe in Pandas python

Question

I have two data frames:

df:

id   string_data
1    My name is Jeff
2    Hello, I am John
3    I like Brad he is cool.

Another data frame named allnames contains a list of names like this:

id  name
1   Jeff
2   Brad
3   John
4   Emily
5   Ross

I want to replace all the words in df that appear in allnames['name'] with "Firstname"

Expected output:

id   string_data
1    My name is Firstname
2    Hello, I am Firstname
3    I like Firstname he is cool.

I tried this:

nameList = '|'.join(allnames['name'])
df['string_data'].str.replace(nameList, "FirstName", case = False))

But it replaces almost 99% of the words

Answer 1

Your solution should working if add words boundaries to Series.str.replace:

nameList = '|'.join(r"\b{}\b".format(x) for x in allnames['name'])
df['string_data'] = df['string_data'].str.replace(nameList, "FirstName", case = False)
print (df)
   id                   string_data
0   1          My name is FirstName
1   2         Hello, I am FirstName
2   3  I like FirstName he is cool.

Or replace values with get and join by dictionary:

d = dict.fromkeys(allnames['name'], 'Firstname')
f = lambda x: ' '.join(d.get(y, y) for y in x.split())
df['string_data'] = df['string_data'].apply(f)
print (df)
   id                   string_data
0   1          My name is Firstname
1   2         Hello, I am Firstname
2   3  I like Firstname he is cool.

EDIT: You can convert all values to lowercase by lower:

d = dict.fromkeys([x.lower() for x in allnames['name']], 'Firstname')
f = lambda x: ' '.join(d.get(y.lower(), y) for y in x.split())
df['string_data'] = df['string_data'].apply(f)